Torque steer experienced by a vehicle driver can be measured by the amount of steering pull, or steering wheel angle change, experienced by a driver independent of the driver's input on the steering wheel. Torque steer is usually experienced in dynamic situations in which a motor vehicle is undergoing acceleration, whether from zero speed, from a slightly higher cruising speed, or even from a much higher cruising speed, depending on the severity of the causation. The causes of torque steer vary greatly, anywhere from unequal length half-shafts, to variations in chassis, suspension or powertrain component/subsystem design, or variations in manufacture and assembly. The appearance of noticeable torque steer ultimately results in driver dissatisfaction.
FIG. 1 depicts a conventional, prior art power steering system 100 utilized on motor vehicles equipped with variable effort steering. At Block 102, input are steering assist parameters 102, at least, for example, vehicle speed, which are then supplied to a power steering assist controller 104, the controller commonly being associated with an hydraulic steering assist. The controller 104 then predicts, through a predetermined electronic routine, the amount of steering assist to supply to a power steering column 110 via a coil 108 on the power steering column by generating a steering assist signal 106. The power steering column 110 is directly connected to the vehicle steering wheel 112, whereat the driver inputs his/her vehicle turning commands into the power steering column.
For example, at high vehicle cruising speeds, the power steering assist controller 104 decreases steering assist via the steering assist signal 106 to the coil 108, resulting in a stiffer steering wheel rotation as felt by the driver as the driver rotates the steering wheel 112 incorporated in power steering column 10. Whereas at zero, or low, vehicle speeds, the power steering assist controller 104 increases steering assist via the steering assist signal 106 to the coil 108 resulting in a looser steering wheel rotation as felt by the driver as the driver rotates the steering wheel 112.
Existing conventional methods of correcting torque steer on (hydraulic) power steered motor vehicles equipped with variable effort steering can be quite costly, as for example, intermediate driveshafts, modifying engine mounting technology/methods, modifying chassis or suspension design and manufacturing. Examples of methods of torque steer are outlined in U.S. Pat. Nos. 6,032,755; 6,505,702; and 6,591,937.
Accordingly, what is needed in the art is a simpler, cost effective method for addressing torque steer on (hydraulic) power assist steered motor vehicles equipped with any form of variable effort steering